1. Field of the Invention
The present invention relates to a sealing apparatus and a sealing method for a flat-type cathode-ray tube and more specifically to a frit coating method and a frit coating apparatus suitable for coating frits on an object to be coated such as glass tube-assembly parts thereof.
2. Description of the Related Art
There is known a reflection type or a transmission type flat cathode-ray tube. The reflection type flat cathode-ray tube, for example, is known in that a manufacturing cost thereof is low and a picture quality thereof is excellent. As shown in FIG. 15 (perspective view), FIG. 16 cross-sectional view) and FIG. 17 (exploded perspective view of a glass tube-assembly), a flat-type cathode-ray tube 1 of this kind has a flat type glass tube-assembly 6 comprised of three members, a first panel, in this example, a front panel 2, a second panel with a fluorescent screen 5 formed thereon, in this example, a screen panel 3, and a funnel 4, which is made by end-sealing an electron gun 8 into a neck portion 7 of the funnel 4.
The front panel 2 is formed of a flat plate-like glass plate, for example. The screen panel 3 includes a curved-surface rising portion, i.e., so-called skirt portion 3a formed along three sides except the joint side of the funnel 4. The funnel 4 is formed like a funnel shape having a large-diameter opening portion at the joint end faces of the two panels 2, 3 and the neck portion 7 joined to the rear portion thereof.
The flat type glass tube-assembly 6 is constructed in such a manner that faces between the front panel 2 and the screen panel 3 are coated with frits by a dispenser, the two panels 2, 3 are fixed by a jig, a joint end face 4A of the funnel 4 is coated with frits, the two panels 2, 3 and the funnel 4 are fixed by a sealing apparatus and are integrally joined by fritting within a furnace.
Heretofore, frits had been coated on the funnel 4 by a dispenser or a roller. However, when frits are coated on the funnel by a roller, an amount of frits adhering to the roller becomes unstable, and there is then a problem that the amount of frits coated on the funnel 4 does not become stable.
In view of the aforesaid aspect, it is an object of the present invention to provide a frit coating method and a frit coating apparatus in which frits can be coated satisfactorily on an object to be coated by stabilizing the amount of frits coated on the object, a coating process can be made efficient and a quality of a product can be stabilized.
Further, as described above, since a flat-type glass tube-assembly 6 of a flat-type cathode-ray tube is comprised of the three members, when this flat-type glass tube-assembly 6 is assembled, first, the front panel 2 and the screen panel 3 are bonded together by frits and then combined with the funnel 4. Accordingly, the front panel 2 and the screen panel 3 need to be temporarily supported in order to butt the front panel 2 and the screen panel 3, which had been butted by frits, with the funnel 4.
However, in a conventional jig for temporarily supporting the front panel 2 and the screen panel 3, i.e., so-called sealing jig, a plate spring attached to an annular holding member is directly urged against the front panel 2 and the screen panel 3. At that time, in the screen panel 3, since the plate spring is brought in contact with a curved portion having a large curved angle, there does not arise any problem. However, since the plate springs of the edge portions at both sides are brought in contact with the flat plate-like front panel 2, there is then a risk that the front panel will be damaged or cracked.
Specifically, the edge portion of the flat plate-like front panel is chamfered. When the metal plate spring is directly urged against the edge portion of the chamfered front panel to thereby hold the front panel and the screen panel, the chamfered portion is damaged by scratches such as micro-cracks. When the front panel is sintered by frits within a furnace, a stress occurs in the front panel and the micro-crack grows to become a large crack so that the front panel will be broken. There is then a problem that the front panel cannot be sintered by frits safely.
In view of the aforesaid aspect, it is another object of the present invention to provide a sealing apparatus for a flat-type cathode-ray tube in which glass tube-assembly parts can be prevented from being damaged and a flat-type glass tube-assembly can be sintered together, a sealing jig for such sealing apparatus and a sealing method.
In a frit coating method according to the present invention, frits supplied from a frit supply means are coated on a predetermined portion of an object to be coated by a roller-type coating means.
According to the frit coating method of the present invention, frits are coated by the roller-type coating means, thereby the amount of frits supplied to the roller-type coating means is stabilized, the amount of frits coated on the object to be coated is stabilized and frits can be coated satisfactorily.
A frit coating apparatus according to the present invention comprises a frit supply means for supplying frits, a roller-type coating means for supplying frits to an object to be coated and a moving means for moving the object to be coated in a close relation to the roller-type coating means.
Since the frit coating apparatus according to the present invention has the arrangement in which the object to be coated is moved by the moving means in a close relation to the roller-type coating means to which frits had been supplied, the amount of frits coated on the object to be coated can be made stable and thereby frits can satisfactorily be coated on the object to be coated.
A sealing jig according to the present invention includes a holding means for holding a front panel and a screen panel by frits such that joint surfaces of the front panel and the screen panel are butted with each other, wherein the holding means is provided with a first resilient member which is urged against the outer surface of the front panel and a second resilient member which is urged against the outer surface of the screen panel, and a portion in which the first resilient member comes in contact with the front panel is formed of a member whose hardness is selected to be less than that of the front panel.
In the sealing jig according to the present invention, since the holding means holds the combined assembly in which the front panel and the screen panel are butted with each other by urging the first resilient member and the second resilient member against the outer surfaces of the front panel and the screen panel, respectively, the front panel and the screen panel can reliably be held without positional displacement. In addition, since the portion in which the first resilient member is urged against the outer surface of the front panel is comprised of the member whose hardness is selected to be less than that of the front panel, the front panel can be protected from being damaged by the member, and the occurrence of cracks and the like can be prevented when the glass tube-assembly is sintered by frits.
A sealing apparatus according to the present invention is comprised of a frame for properly positioning a combined assembly in which a front panel, a screen panel and a funnel are butted with each other by frits and the above sealing jig.
Since the sealing apparatus according to the present invention includes the frame for properly positioning the combined assembly in which the front panel, the screen panel and the funnel are butted with each other by frits and the above sealing jig, the three of the front panel, the screen panel and the funnel can be sealed together. In addition, since the sealing apparatus includes the above sealing jig, the front panel can be protected from being damaged and the occurrence of cracks and the like can be prevented when the glass tube-assembly is sintered by frits. Then, it becomes possible to sinter the glass tube-assembly by frits safely.
A sealing method according to the present invention comprises the steps of butting joint surfaces of a front panel, a screen panel and a funnel and holding and sealing the front panel, the screen panel and the funnel under the condition that an angle between a plane of the front panel and a horizontal plane becomes an acute angle.
In the sealing method according to the present invention, since the front panel, the screen panel and the funnel are held and sealed under the condition that the angle between the plane of the front panel and the horizontal plane becomes the acute angle, when fused frits are caused to flow by a gravitation, such fused frits are stored in a three-point joint portion in which the front panel, the screen panel and the funnel are collected, and hence the front panel, the screen panel and the funnel can reliably be sealed by frits. Therefore, the air leakage at the three-point joint portion can be prevented reliably.